1. Field of the Invention
The present invention relates to computer systems, and more particularly, but not by way of limitation, to computer system utilizing semaphores implemented in the system I/O and controlled, at least in part, by an application specific integrated circuit also implemented in the system I/O.
2. Description of Related Art
Networks serve the purpose of connecting many different personal computers (PCs), workstations, or terminals to each other, and to one or more host computers, printers, file servers etc., so that expensive computing assets, programs, files and other data may be shared among many users.
In a network utilizing a client/server architecture, the client (personal computer or workstation) is the requesting machine and the server is the supplying machine, both of which may preferably be connected via the network, such as a local area network (LAN), wide area network (WAN) or metropolitan area network (MAN). This is in contrast to early network systems that utilized a mainframe with dedicated terminals.
In a client/server network, the client typically contains a user interface and may perform some or all of the application processing and as mentioned above can include personal computer or workstations. The server in a client/server network can be high-speed microcomputers or minicomputers and in the case of a high-end server can include multiple processors and mass data storage such as multiple CD-ROM drives and multiple hard drives, preferably with redundant array of inexpensive disk (RAID) protection. An exemplary server such as a database server maintains the databases and processes requests from the client to extract data from or update the database. An application server provides additional business processing for the clients. The network operating system (NOS) together with the database management system (DBMS) and transaction monitor (TP monitor) are responsible for the integrity and security of the server.
Client/server networks are widely used throughout many different industries and business organizations, especially where mission-critical applications requiring high performance are routinely launched. The mass storage and multi-processing capabilities provided by current client/server network systems (for example, the high-end servers) that run such applications permit a wide range of essential services and functions to be provided through their use.
As can be appreciated, many of businesses are highly dependent upon the availability of their client/server network systems to permit essential network services and functions to be carried out. As client/server network systems become increasingly essential to the everyday operations of such businesses, additional steps need to been taken in the design and construction of the server in the client/server network system to ensure its continuous availability to the clients. That is to say, in the design and construction of a server, steps need to be taken to ensure that the server can be operated with little or no downtime.
It can be appreciated by those skilled in the art that high availability, reliability and serviceability are valuable design aspects in ensuring that a server is a "zero downtime" system that will operate with little or no downtime. The modularity of components within a server has been recognized as an important design consideration in ensuring that the downtime of a server will be minimized. Modules can be removed and examined for operability or other purposes much easier than permanently mounted fixtures within a server chassis. When various components of a server can be provided in a modular form, they can also be readily replaced to maintain the operational status of the server with minimal downtime.
Removable modular components may include disc drives and power supplies. As described above, the removability of modular components allows for better overall serviceability of the computer system which is a distinct advantage. For example, a defective power supply in the server generally requires prompt replacement in order to limit downtime. Modular components and connectors facilitate prompt replacement and are thus popular in many computer designs.
Originally, a rule of practice in the maintenance of modular components or printed circuit boards of a server was that of turning the power to the server off before any modular components or printed circuit boards were removed from or added to the chassis or support frame of the server. Recent innovations have centered around a highly desirable design goal of"hot-pluggability" which addresses the benefits derived from inserting and removing modular components and printed cards from the chassis of the server when the server is electrically connected and operational. It can be readily appreciated that modularization and hot-pluggability can have a significant bearing on the high availability aspect of a high-end server.
Hot-pluggable components may include storage or disc drives, drive cages, fans, power supplies, system I/O boards, control boards, processor boards, and other sub-assemblies. The ability to remove these constituent components without having to power down the server allows for better overall serviceability of the system, which is a distinct advantage to both the user and the maintenance technician.
Component redundancy has also been recognized as an important design consideration in ensuring that a server will operate with little or no downtime. Essentially, component redundancy is typically provided in a system to better ensure that at least one of the redundant components is operable, thereby minimizing the system down time. With component redundancy, at least two components are provided that can perform the same function, such that if one of the components becomes faulty for some reason, the operation fails over to the redundant component. When at least one of the redundant components is operable, continued operation of the computer system is possible even if others of the redundant components fail. To further enhance reliability and serviceability, redundant components have been made hot pluggable.
Dynamic reconfiguration of a server system can also be accomplished by providing upgradable modular components therein. As can be readily appreciated, this objective can be accomplished by the addition or substitution of components having different circuits, preferably updated or upgraded, disposed therewithin. When components are redundant and hot pluggable, reconfiguration of the server is often possible without taking the server offline.
Another important design aspect with respect to providing redundant and hot pluggable components in a server system is to ensure and maintain a safe working environment while the server is operating and being repaired or upgraded. Accordingly, when the system components are swapped or upgraded, the exposure of hot connectors and contacts must be kept to a minimum. It can be appreciated by those skilled in the art that further developments in this area would significantly enhance the reliability and serviceability aspects of a high-end server system.
To further enhance the serviceability of server systems, additional innovations may be required in the design and construction of diagnostic sub-systems thereof. In existing client/server network systems it is often difficult to obtain, in a timely manner, important diagnostic data and information corresponding to a component failure in order to facilitate the quick serviceability of the server. Therefore, it can be appreciated that the more information that can be readily provided to locate a defective component or problem with the server, the better the optimization of the amount of time the server is up and running.
Although multiprocessors enhance the performance of the computer system, the multiple processors also create additional problems. One of the problems that has been encountered with multiprocessor systems occurs when more than one of processors attempts to access a shared hardware or software resource at the same time. One common solution to this problem is through the utilization of system memory semaphores. In general, semaphores are counters used to control access to shared resources by multiple processes. Semaphores are commonly used as a locking mechanism to prevent processes from accessing a particular resource while another process is performing operations on it.
An example of existing semaphore use is illustrated in the computer system 300 depicted in FIG. 3. As depicted the computer system 300 includes: CPUs 310 and 312; system memory 314, which includes semaphore 318; and system input/output (I/O) 316. The components of computer system 300 are coupled in communication through common bus 320. In operation, for example, if CPU 310 wants to access a resource of system I/O 316, if first much check the status of the desired resource by sending a read command over bus 320 to the associated semaphore 318 in the system memory. The semaphore 318 returns the status information back to CPU 310. If the desired resource is available, CPU 310 sends a write command to semaphore 318 to change the status of semaphore 318 from available to unavailable. To prevent another process or processor from checking the status of semaphore 318 concurrent with CPU 310, prior to sending the read command, CPU 310 will lock bus 320 until the read, write routine is completed.
As can be appreciated, not only does locking bus 320 prevent another processor or master from accessing the particular semaphore, but it also prevents the other processors from communicating with the other devices on the bus. As further illustrated in FIG. 3, the semaphore 318 is implemented in the system memory as is historically done with most semaphore applications. Although application software can communicate with the system memory very readily, there are many other drivers, such as a ROM BIOS function call,and processes in Systems Management Interrupt (SMI) mode that can not.
Generally, communicating with the system memory space requires protection, and often protected operating systems implement disjointed memory spaces and give disjointed memory spaces to multiple devices. Therefore, it is problematic to create a common area for multiple processes to communicate by setting a flag. This is because the common area cannot be protected by the standard method of protection provided and required by the operating system. The standard method of protection allows a particular process to access only a particular memory region. Therefore, the only way to create a common area for the multiple processes is to intermingle memory regions, which can cause numerous problems.